Post-primary tuberculosis, also known as reactivation tuberculosis or secondary tuberculosis Is perhaps more correctly designated “tuberculosis in an immunocompetent host” 1. The features are distinctly different to so-called primary tuberculosis which occurs in the absence of immunity.
Pathology
Location
As explained by high oxygen tension and impaired lymphatic drainage, typically there is involvement of:
- apical and posterior segments of the upper lobe
- superior segment of lower lobe
Radiographic features
CT
Parenchymal disease
- ill-defined patchy consolidation
- clustered parenchymal opacification may give rise to a galaxy sign
- cavitation usually develops within the consolidation
- fibroproliferative disease with coarse reticulonodular densities
- endobronchial spread with "tree-in-bud" appearance, best appreciated on HRCT
- healing results in fibrosis, volume loss and traction bronchiectasis
- lymphadenopathy occurs only in 5% cases
Airway disease
Central airway involvement results in bronchial stenosis which may lead to lobar collapse associated with traction bronchiectasis and mucoid impaction.
Pleural disease
- occurs in a minority of cases (18%)
- small pleural effusion
- pleural thickening
- pleural calcification
Chest wall involvement
Chest wall involvement occurring due to direct extension from pulmonary disease manifests as bone and/or cartilage destruction and cutaneous fistula formation.
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